The protection of ground water and natural bodies of water requires systems for diverting and/or treating water that contacts roadways, parking lots, and other man-made structures. If such diversion or treatment systems are not provided, particulates and other contaminants located on or forming part of such structures may be carried by drain water or stormwater to the natural water bodies and contaminate them. Local, state and federal laws and rules require municipalities, businesses and, in some instances, private entities, to establish means to reduce particulate and contaminant levels permissibly transferred to natural bodies of water from property under their control. Particular requirements may vary from jurisdiction to jurisdiction, but all are likely to become more, rather than less, stringent.
Most new land development plans and upgrades to existing paved surfaces involve the insertion of a preliminary separation system, generally for connection to the municipal water-handling infrastructure. Any preliminary separation system should be designed with the capability to receive fluid flowing in at a wide range of rates. It is desirable, then, to have a separation system capable of handling variable fluid flow rates with reduced likelihood of backup and flooding of the surface above. It is also desirable to control the flow through the system such that trapped particulates are not scoured or washed out of the device and re-entrained during high flows for passage downstream.
A variety of stormwater separation systems exist. These systems generally include a tank or container including a storage or treatment chamber within which, ideally, floating particulates are retained, and non-floating particulates are allowed to settle. The storage chamber includes an inlet for receiving untreated water, and an outlet for movement of treated water out of the chamber. The tank may also include a bypass arrangement to allow excess untreated water to exit the tank without passing through the storage chamber. In one implementation of such systems the storage chamber is located in a lower part of the tank and the bypass is located in an upper part of the tank, with an insert or deck located within the tank to separate the two chambers, the insert having one opening that defines the storage chamber inlet and another opening that defines the storage chamber outlet.
The device shown in U.S. Pat. No. 7,666,303 is exemplary of such a separator and utilizes a T-shaped drop tube at the storage chamber inlet to direct inflows into the storage chamber, a riser tube at the storage chamber outlet to define a floatables collection area in the upper part of the storage chamber and a weir atop the insert to direct incoming stormwater to the storage chamber. As flows through the storage chamber of such a separator system are increased (e.g., by raising the height of the weir), less stormwater flow bypasses, but potential for scouring and washout within the storage chamber increases.
Accordingly, it would be desirable to provide a separator with increased treatment flow capacity while at the same time incorporating one or more cost-effective features to limit scouring and washout.